PartitionReplicaListener should return execution to partition thread pool after calls to PlacementDriver

Futures returned by the PlacementDriver might be completed in the Metastorage watch threads, which are critical and hence should not be used for heavy (potentially I/O-bound) computations which are possible when accessing storages. So after such futures complete, the control should be returned to the partition-operations executor.

IGNITE-21079 fixes this for calls to SchemaSyncService and RaftGroupService by introducing decorators around them. The same should be done for calls to PlacementDriver.